CI: Split setup, linter and build in separate steps

Make sphinx-build treat warnings as errors.

(And fix last remaining warning missed in #3795.)

.github/workflows/ci.yml

@@ -8,16 +8,20 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
 
-      - name: Lint and build documentation
+      - name: Install dependencies
         run: |
           # Install tools used by `_tools/format.sh`.
-          sudo apt-get update -qq
-          sudo apt-get install -qq dos2unix recode
-          # Append the `PATH` so we can run `codespell`.
-          export PATH="$HOME/.local/bin:$PATH"
-          pip3 install -r requirements.txt
-          pip3 install codespell
+          sudo apt-get -qq update
+          sudo apt-get -qq install dos2unix recode
+          sudo pip3 install -r requirements.txt
+          sudo pip3 install codespell
+
+      - name: Linter checks
+        run: |
           bash _tools/format.sh
           codespell -I _tools/codespell-ignore.txt {about,community,development,getting_started,tutorials}/**/*.rst
+
+      - name: Sphinx build
+        run: |
           # Use dummy builder to improve performance.
-          sphinx-build --color -b dummy -d _build/doctrees . _build/html
+          sphinx-build --color -b dummy -d _build/doctrees -W . _build/html

tutorials/3d/csg_tools.rst

@@ -249,7 +249,7 @@ or a city; explore its limitations when designing your game.
 Using prototype textures
 ------------------------
 
-Godot's :ref:`doc_spatial_material` supports *triplanar mapping*, which can be
+Godot's :ref:`doc_standard_material_3d` supports *triplanar mapping*, which can be
 used to automatically apply a texture to arbitrary objects without distortion.
 This is handy when using CSG as Godot doesn't support editing UV maps on CSG
 nodes yet. Triplanar mapping is relatively slow, which usually restricts its